Heat-resistant photoresist composition and negative-type pattern formation method

ABSTRACT

A heat-resistant negative-working photoresist composition comprising a resin component having a carbodiimide unit in the molecule, and a compound capable of inducing a basic compound by irradiation with actinic rays. The photosensitive layer formed by the photoresist composition shows a sufficient sensitivity even by a lower irradiation energy and can give a sharp negative-type pattern by irradiation with actinic rays such as ultraviolet rays.

FIELD OF THE INVENTION

The present invention relates to a heat-resistant photoresistcomposition and a method of forming a negative-type pattern.

BACKGROUND OF THE INVENTION

Hitherto, from the points of mechanical strength and heat-resistantcharacteristics, a photoresist using a polyimide or a polyimideprecursor has been practically used as a heat-resistant photoresist, andin particular, a negative-working photoresist forming desired reliefimages on various kinds of substrates by reducing solubility of thepolyimide or polyimide precursor to a developer by irradiation ofactinic rays has been mainly used.

Such heat-resistant photoresists each using negative-workingphotosensitive polyimide or the precursor thereof, which leave portionsirradiated with actinic rays on each substrate, and the uses thereof aremuch proposed. For example, there are proposed (1) a method ofintroducing a methacryloyl group into a polyimideprecursor via an esterbond or an ionic bond as described in JP-A-49-11541, JP-A-50-40992,JP-A-54-145794, JP-A-56-38038, etc., ("JP-A" as used herein means an"unexamined published Japanese patent application"), (2) a method ofusing a soluble polyimide having a photopolymerizing olefin as describedin JP-A-59-108031, JP-A-59-220730, JP-A-59-232122, JP-A-60-6729,JP-A-60-72925, JP-A-61-57620, etc., and (3) a method of using aself-sensitizing type polyimide having a benzophenone skeleton andhaving an alkyl group at the ortho-position of the aromatic ring havingbonded thereto a nitrogen atom as described in JP-A-59-219330,JP-A-59-231533, etc.

However, in the conventional negative-working photoresists using theabove-described photosensitive polyimide or polyimide precursor, thereis a problem in the function and the resolving power thereof andfurther, according to the uses thereof, there is a problem that theyield for the negative-working photoresist at the production thereof islowered, etc. For example, in the heat-resistant photoresists producedin the method (1) described above, in the case of the ester bond-typephotoresist, the synthesis is difficult, and in the case of the ionicbond-type photoresist, shrinkage occurs at imidation (heat curing).Also, in these heat-resistant photoresists, the thickness of the film orthe layer of the photoresist is reduced at development, and thethickness of the residual film or layer after development and heatcuring becomes about 50% of the initial thickness of the film or thelayer. That is, there is a problem in the dimensional stability in theseheat-resistant photoresists. Moreover, in the heat-resistantphotoresists produced by the methods (2) and (3) described above, sincethe structure of the skeleton of the polymer used is limited, theproperties of the coated layer or film finally obtained, whereby thesephotoresists cannot flexibly correspond to various requiredcharacteristics.

Further, since these photosensitive polyimides and polyimides precursorsare insufficient in the point of light transmittance and, in particular,the light transmission factor in the film thickness direction isinsufficient, several hundreds of mJ/cm² are required as the amount ofultraviolet rays irradiating for forming patterns. As a result, theexposure time is prolonged and thus they have yet a problem in the pointof productivity.

On the other hand, polycarbodiimide having a carbodiimide unit in themolecule is known as a resin excellent in heat resistance obtained bydecarboxylation polycondensation of an isocyanate compound. By heatingthe resin, the carbodiimide bond in the molecule thereof causes acrosslinking reaction to improve the heat resistance of the resin.

Recently, a photosensitive composition obtained by compounding such apolycarbodiimide with an aromatic azide compound is proposed asdescribed in JP-A-6-211956. However, this composition has thedisadvantages that the composition is yet insufficient in the point ofsensitivity, at the irradiation of the aromatic bisazide compound withlight it is necessary to sufficiently consider the influence of oxygen,and thus, in the case of using the composition, the system is liable tobe restricted in the apparatus. That is, since when a large amount ofoxygen exists in the atmosphere at the light irradiation, nitrene formedby the light irradiation of the bisazide compound does not react withthe polymer but preferentially reacts with oxygen to greatly lower thesensitivity of the composition, a deaerator becomes necessary at thelight irradiation. Also, the coated film formed from the photosensitivecomposition compounded with an aromatic bisazide compound is greatlycolored, and therefore it is difficult to use such a photosensitivecomposition in the field of requiring a transparency, such as aphotosemiconductor device, LCD, etc. Further, there are the faults thatthe mechanism of the curing reaction is complicated, and the coated filmbecomes brittle and is poor in flexibility after the light irradiation.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to overcome theabove-described problems caused by conventional negative-workingphotoresists and to provide a heat-resistant photoresist compositionhaving a high sensitivity and a good resolving power and sufficientlycapable of enduring practical use.

Another object of the present invention is to provide a method offorming a negative-type pattern by irradiating a photosensitive layerformed with the heat-resistant composition with actinic rays via aphotomask followed by development.

As a result of various investigations on a novel heat-resistantphotoresist composition capable of attaining the objects describedabove, it has been found that a photoresist composition usingpolycarbodiimide as the skeletal component of the photoresist andcompounding therewith a carbamate derivative as a compound(photodecomposable base generator) capable of inducing a basic compoundby the irradiation of actinic rays has excellent sensitivity andresolving power and forms a negative-working relief image showing lessreduction in the thickness of the coated layer thereof. The presentinvention has been completed based on this finding.

According to one embodiment of the present invention, there is provideda heat-resistant photoresist composition comprising a resin componenthaving a carbodiimide unit represented by the following formula (I) inthe molecule, and a compound capable of inducing a basic compound by theirradiation of actinic rays.

    .brket open-st.R-N=C=N.brket close-st.                     (I)

wherein R represents a divalent organic group.

According to another embodiment of the present invention, there isprovided a method of forming a negative-type pattern, which comprisesirradiating a photosensitive layer formed using the heat-resistantphotoresist composition with actinic rays via a photomask, applyingthereto a heat treatment, and removing unexposed portions with adeveloper.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail below.

The resin component used in the heat-resistant photo-resist compositionof the present invention is a compound having a carbodiimide unitrepresented by the formula (I) described above in the molecule, that is,a polycarbodiimide compound, which becomes the skeletal material of aresist film formed. Conventional methods can be used as a method ofsynthesizing such a polycarbodiimide. For example, the polycarbodiimidecan easily be synthesized by reacting organic polyisocyanates each otherin an organic solvent in the presence of a carbodiimidation catalyst asdescribed in, for example, T. W. Campbell et al., Journal of OrganicChemistry, 28, 2069(1963), L. M. Alberino et al, Journal of AppliedPolymer Science, 12, 1999(1977), JP-A-2-292316, and JP-A-4-275359.

Examples of the organic polyisocyanate which can be used in thesynthesis of the polycarbodiimide include 2,4-tolylene diisocyanate,2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate,4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethanediisocynate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate,4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'diphenyletherdiisocyanate, and o-tolylene diisocyanate. Those compounds can be usedalone or as mixtures of two or more thereof (a copolymer is obtained).

Examples of the organic solvent which can be used include halogenatedhydrocarbons such as tetrachloroethylene, 1,2-dichloroethane,chloroform, etc.; ketones such as acetone, methyl ethyl ketone, methylisobutyl ketone, cyclohexanone, etc.; and cyclic ethers such astetrahydrofuran, dioxane, etc. Those can be used alone or as mixturesthereof.

Examples of the carbodiimidation catalyst which can be used includephosphorene oxides such as 3-methyl-1-phenylphosphorene-1-oxide,1-phenyl-2-phosphorene-1-oxide, 1-ethyl-2-phosphorene-1-oxide, etc., andthe 3-phosphorene isomers of them. Those can be used alone or asmixtures thereof.

The molecular weight of the polycarbodiimide used in the presentinvention can be controlled by blocking the chain thereof by introducinga monoisocyanate to the terminal thereof. The preferred molecular weightof the polycarbodiimide in the present invention is from about 300 to300,000, and preferably from about 2,000 to 50,000, as a number averagemolecular weight (GPC (gas permeation chromatography) method, convertedas polystyrene). If the number average molecular weight thereof is lessthan 300, there is a possibility that the mechanical strength of thecoated film finally obtained becomes low. On the other hand, if thenumber average molecular weight is over 300,000, there is a possibilitythat the storage stability thereof in a solution state becomes poor.

The polycarbodiimide used in the present invention may contain otherstructural unit such as an amic acid unit, an imide unit, an amidoimideunit, a siloxane unit, etc., so long as the polycarbodiimide has thecarbodiimide unit represented by the formula (I) described above in themolecule.

The content of the carbodiimide unit in the resin component is from 20to 100 mol %, and preferably from 50 to 95 mol %. If the content of theunit is less than 20 mol %, the resolving power of the negative-typepattern formed is undesirably reduced.

The heat-resistant photoresist composition of the present inventioncontains a compound capable of inducing a basic compound by irradiatingthe resin component with actinic rays as an essential component. Such acompound has a property that when the compound is irradiated withactinic rays such as ultraviolet rays, the hydrogen atom is pulled outfrom the molecule of the compound to liberate a basic material such asan amine, and is generally called "photo-base generator","photodecomposable base generator", "amine photo-generator", etc.Practically, as the compound it is preferred to use a carbamatederivative represented by the following formula (II) and/or a carbamatederivative represented by the following formula (III). ##STR1## whereinR₁, R₂, and R₃ each represent a hydrogen atom or a methoxy group; R₄ andR₅ each represent a hydrogen atom or a nitro group, and at least one ofR₄ and R₅ shows a nitro group; R₆ represents a hydrogen atom or a loweralkyl group having from 1 to 6 carbon atoms; and X represents amonovalent amine residue for carbamate bonding. ##STR2## wherein R₁, R₂,and R₃ each represent a hydrogen atom or a methoxy group; R₄ and R₅ eachrepresent a hydrogen atom or a nitro group, and at least one of R₄ andR₅ shows a nitro group; R₆ represents a hydrogen atom or a lower alkylgroup having from 1 to 6 carbon atoms; and Y represents a divalent amineresidue for dicarbamate bonding.

In the present invention, when the photosensitive layer formed from thephotoresist composition containing the above-described resin componentand the above-described compound capable of inducing a basic compound byirradiation with actinic rays as the essential components is irradiatedwith actinic rays, the solubility of the exposed portions of the resincomponent to a developer is lowered as compared with the solubilitythereof before the irradiation, whereby a desired negative-type patterncan be obtained.

The reason thereof has not yet been clarified, but it is considered thatthe carbamate derivative forms free primary amine or secondary amine byirradiation with actinic rays and the amine thus formed acts on thecarbodiimide unit in the resin component to induce a crosslinkingreaction, whereby the solubility of the resin component to the developeris lowered. Practically, a nucleophilic addition reaction, etc., ofamine occurs at the carbon of the carbodiimide, and in the induction ofthe crosslinking reaction, an amine addition product of the carbodiimideunit, such as guanidine derivatives, urea derivatives, etc., is formed.It is also considered that the addition product catalytically functionsto further synergistically and chainlike accelerate the crosslinkingreaction. Further, for more accelerating such a crosslinking reactionaccompanied by the change of solubility, it is preferred to carry out aheat treatment at the temperature of from 50° to 300° C., and preferablyfrom 100° to 170° C., for about 5 to 30 minutes after exposure (beforedevelopment). If the heat treatment is carried out at a temperature over300° C., there are undesirable possibilities that the carbamatederivative is thermally decomposed, the carbodiimide bonds in the resincomponent are crosslinked and cured by forming a dimer or a trimer togreatly prolong the development time, and also the contrast (resolvingpower) of the pattern obtained is lowered.

When at least one of R₁, R₂, and R₃ in the formula (II) or (III)described above is a methoxy group, the absorption region of thephotoresist composition containing the compound represented by theformula to actinic rays such as ultraviolet rays is shifted to a longwavelength side, whereby the exposure sensitivity of the photoresistcomposition is preferably improved. Further, when at least one of R₄ andR₅ in the formula (II) or (III) is a nitro group, the generationefficiency of an amine at the irradiation with actinic rays isincreased. Also, R₆ in the formula (II) or (III) is a hydrogen atom or alower alkyl group having from 1 to 6 carbon atoms, and in particular,when R₆ is a methyl group or an ethyl group, the generation efficiencyof amine at the irradiation with actinic rays is preferably moreincreased.

Such carbamate derivatives represented by the formulae (II) and (III)can be synthesized by the methods described in J. F. Cameron and J. M.J. Frechet, Journal of the Americal Chemical Society, 1991, 113, 4303and G. Ciamician and P. Silber, Ber., 1901, 34, 2040.

The monovalent amine residue represented by X in the formula (II) makescarbamate bonding, and primary amines and secondary amines can be usedas the amine residue. Such amines are preferably amines which havesufficiently high basicity, are solid or liquid at normal temperatureand have high boiling point so that the amines are difficult tovolatilize off at heating after exposure. Examples of the amines arecyclohexylamine, piperidine, 2,6-dimethylpiperidine, quinoline and thederivatives thereof, aniline and the derivatives thereof, imidazole andthe derivatives thereof, etc.

On the other hand, the divalent amine residue represented by Y in theformula (III) makes carbamate bonding, and primary amines and secondaryamines can be used as the amine residue. Such amines are preferablyamines which have high boiling point and are solid or liquid at normaltemperature, similar to the above-described amines. Examples of theamines are hexamethylenediamine, p-xylylenediamine, p-phenylenediamine,m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylether, 2,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether,4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone,3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl sulfide,3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide,3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone,4,4'-diaminobenzophenone, 4,4'-diaminodiphenylpropane,3,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane,4,4'-diaminodiphenylhexafluoropropane,3,4'-diaminodiphenylhexafluoropropane,3,3'-diaminodiphenylhexa-fluoropropane,bis[4-(3-diaminophenoxy)phenyl]methane,bis[4-(4-aminophenoxy)phenyl]methane,2,2-bis[4-(3-aminophenoxy)phenyl]propane,2,2-bis[4-(4-aminophenoxy)phenyl]propane,2,2-bis[4-(3-aminophenoxy)phenyl]hexafluoropropane,2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane,1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl,bis[4-(3-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(4-aminophenoxy)phenyl]sulfone,bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether,etc.

Particularly preferred compounds in the carbamate derivatives arecompounds having following structures [PBG-1], [PBG-2], [PBG-3], and[PBG-4]. ##STR3##

The heat-resistant photoresist composition of the present invention ischaracterized in that the resin composition having the structural unitrepresented by the formula (I) described above contains a compoundgenerating a base such as an amine by irradiation with actinic rays, anda negative type pattern is formed by exposing and developing the layerof the heat-resistant photoresist composition. Also, if necessary, theheat-resistant photoresist composition can be compounded withconventional sensitizers.

The carbamate derivative is compounded with the resin component havingthe carbodiimide unit represented by the formula (I) in an moleculethereof in the amount of from 0.001 to 100 parts by weight, andpreferably from 0.1 to 50 parts by weight, per 100 parts by weight ofthe resin component. That is, in the present invention, even when theamount of the carbamate derivative is relatively small, the sufficienteffect is obtained. If the compounding amount of the carbamatederivative is less than 0.001 part by weight, the exposure sensitivityof the photoresist composition is lowered, and if the compounding amountthereof is over 100 parts by weight, when a high-temperature heattreatment is applied to the layer of the photoresist composition afterforming a negative type pattern, the residual layer thickness ratio isreduced and the mechanical strength of the photoresist composition layeris lowered, which give bad influences on the properties of thephotoresist composition layer.

A method of forming a negative type pattern using the heat-resistantphotoresist composition of the present invention is specificallydescribed below.

First, a photosensitive liquid is prepared by compounding the resincomponent (polycarbodiimide) synthesized as described above with aphotobase generator such as the carbamate derivative. In this case,organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide,N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, dimethyl sulfide, dimethylsulfone, tetramethylurea, diglyme,triglyme, tetrahydrofuran, dioxane, cyclohexanone, toluene, xylene,halogenated hydrocarbon solvents (methylene chloride, chloroform, carbontetrachloride, etc.), etc., can be used as a diluting solvent. Those canbe used alone or as mixtures thereof.

There is no particular restriction on the amount of the organic solventused, but the solution viscosity in preparing the photosensitive liquidcan be controlled by controlling the amount of the organic solvent used,and thus the viscosity of the photosensitive liquid can be controlled toa viscosity suitable for coating. The amount of the organic solvent usedis generally from 1 to 100 times, and preferably from 2 to 50 times, thetotal amount of the resin component and the photobase generator.

The photosensitive liquid is coated on the surface of a substrate anddried such that the dry thickness of the coated layer becomes from 0.1to 50 μm, and preferably from 1 to 25 μm.

Examples of the substrate which can be used are a rigid substrate suchas a silicon wafer, a glass plate, a copper plate, an aluminum plate, asteel plate, a ceramic plate, etc., and a flexible substrate such as apolyimide film, a polyester film, a copper foil, an aluminum foil, astainless steel foil, etc. In coating the substrate with thephotosensitive liquid, the surface of the substrate can previously beundercoated with a silane coupling agent, a titanate coupling agent,etc., to improve the adhesive property of the substrate.

The photosensitive layer formed by coating the photosensitive liquid onthe substrate followed by drying is usually exposed by irradiating thephotosensitive layer with actinic rays via a photo mask. After exposure,for further improving the difference in solubility between the exposedportions and the unexposed portions, the photosensitive layer thusexposed is, if necessary, heat-treated, whereby the crosslinkingreaction of the exposed portions can be proceeded.

As actinic rays used for the irradiation, it is preferred from the pointof the amount of the irradiation energy to use ultraviolet rays emittedfrom a mercury lamp or excimer laser, but visible light, electron rays,γ-rays, etc., can be used. Since the amount of the irradiation energydiffers according the kind and the compounding amount of the photobasegenerator compounded in the photoresist composition of the presentinvention, the amount thereof cannot be generally determined. However,even a low irradiation energy amount of, for example, from 0.01 to 5,000mJ/cm², and preferably from 0.1 to 500 mJ/m², can be used. In thepresent invention, even in the case of a relatively small irradiationenergy amount, the photosensitive layer shows a sufficientphotosensitivity.

The exposed photosensitive layer is then subjected to a developmentprocess using a dipping method or a spray method to remove theunirradiated portions. In this case, there is no particular restrictionon the developer if the developer can completely dissolve off theunirradiated portions of the photosensitive layer thus exposed in anappropriate period of time. Examples of the developer which can be usedare an organic solvent such as N-methyl-2-pyrrolidone,N,N-dimethylacetamide, N,N-dimethylformamide,1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, dimethyl sulfide,dimethylsulfone, tetramethylurea, diglyme, triglyme, tetrahydrofuran,dioxane, cyclohexane, toluene, xylene, isoamyl acetate,dimethylammonium, halogenated hydrocarbons, etc.; an inorganic alkalineaqueous solution of sodium hydroxide, potassium hydroxide, etc.; and anorganic alkaline aqueous solution of propylamine, butylamine,monoethanolamine, tetramethylammonium hydroxide, choline, etc. Those canbe used alone or as mixtures of them. Those alkaline aqueous solutionscan, if necessary, contain an alcohol or a surface active agent.

After applying the development process, the photosensitive layer thusdeveloped is washed with a rinse liquid, whereby a negative-type imagepattern mainly composed of the resin component having a carbodiimideunit in the molecule can be obtained. Alcohols such as methanol,ethanol, isopropanol, etc., or water, etc., can be used as the rinseliquid.

As described above, since the heat-resistant photoresist composition ofthe present invention uses the specific resin component having thecarbodiimide unit in the molecule and also uses a compound(photodecomposable base generator) inducing a basic compound byirradiation with actinic rays, the photoresist composition shows asufficient sensitivity even in the case of a low irradiation energyamount and also has the excellent effects that the transparency, theresidual layer thickness ratio, the flexibility, and the resolving powerof the pattern obtained are excellent as compared with conventionalphotoresist compositions.

The present invention is described in more detail by the followingexamples, wherein all parts, unless otherwise indicated, are by weight.

Synthesis Example 1

To 500 g of toluene was added 100 g of tolylene diisocyanate togetherwith 0.58 g of 3-methyl-1-phenylphosphorene-1-oxide as acarbodiimidation catalyst, and the reaction was carried out at 100° C.for 6 hours to synthesize a solution of polycarbodiimide A.

Synthesis Example 2

To 500 g of tetrahydrofuran was added 100 g of 4,4'-diphenylmethanediisocyanate together with 0.58 g of3-methyl-1-phenylphosphorene-1-oxide as a carbodiimidation catalyst andthe reaction was carried out at 100° C. for 6 hours to synthesizepolycarbodiimide B.

EXAMPLE 1

To the solution of the polycarbodiimide A obtained in Synthesis Example1 was added the compound PBG-1 described above as a photodecomposablebase generator in an amount of 10 parts per 100 parts of thepolycarbodiimide resin component, the resulting mixture was uniformlymixed with stirring, and insoluble matters were removed by filtration toobtain a solution (photosensitive liquid) of the heat-resistantphotoresist composition of the present invention.

The photosensitive liquid thus prepared was spin-coated on a siliconewafer and dried to form a photosensitive layer having a thickness of 3μm.

The photosensitive layer was exposed through a glass mask by irradiatingthe layer with actinic rays having a wavelength of 365 nm emitted from asuper high-pressure mercury lamp of 250 W having a glass filter coveredthereon. After exposure, the photosensitive layer was post-heated at120° C. for 5 minutes, developed with toluene heated to 40° C. as adeveloper for one minute, and then rinsed with 2-propanol to obtain anegative-type sharp pattern composed of the light-irradiated portionsonly remaining on the silicone wafer.

The photosensitive layer had a sensitivity of 50 mJ/cm² and showed aresolving power (aspect ratio) of 1.12, that is, the photosensitivelayer had a very high sensitivity and showed a very high resolvingpower. Further, the light transmittance of the pattern thus formed at400 nm was 75%, which showed the pattern having a transparency. When thepattern was heat-treated at 260° C. for one hour, the residual layerthickness ratio was 90%, and the extent of the heat shrinkage thereofwas less.

EXAMPLE 2

By following the same procedure as in Example 1 except that 7.5 parts ofthe compound PBG-2 described above was used in place of 10 parts of thecompound PBG-1 as the photo-decomposable base generator used in Example1, the heat-resistant photoresist composition of the present inventionwas prepared, and a negative-type pattern was formed in the same manneras in Example 1.

The photosensitive layer thus obtained had a sensitivity of 60 mJ/cm²and showed a resolving power (aspect ratio) of 0.92, that is, thephotosensitive layer had a very high sensitivity and showed a very highresolving power. Further, the light transmittance of the pattern at 400nm was 73%, which showed the pattern having a transparency. When thepattern was heat-treated at 280° C. for one hour, the residual layerthickness ratio was 87%, and the extent of the heat shrinkage thereofwas less.

EXAMPLE 3

By following the same procedure as in Example 1 except that 6.4 parts ofthe compound PBG-3 described above was used in place of 10 parts of thecompound PBG-1 as the photodecomposable base generator used in Example1, the heat-resistant photoresist composition of the present inventionwas prepared and a negative-type pattern was prepared in the same manneras in Example 1.

The photosensitive layer thus obtained had a sensitivity of 40 mJ/m² andshowed a resolving power (aspect ratio) of 0.86, that is thephotosensitive layer had a very high sensitivity and showed a very highresolving power. Further, the light transmittance of the pattern at 400nm was 78%, which showed the pattern having a transparency. When thepattern was heat-treated at 280° C. for one hour, the residual layerthickness ratio was 92% and the extent of the heat shrinkage thereof wasless.

EXAMPLE 4

By following the same procedure as in Example 1 except that the solutionof the polycarbodiimide B obtained in Synthesis Example 2 was used andalso N-methyl-2-pyrrolidone was used as the developer, theheat-resistant photoresist composition of the present invention wasprepared, and a negative-type pattern was prepared in the same manner asin Example 1.

The photosensitive layer thus obtained had a sensitivity of 70 mJ/m² andshowed a resolving power (aspect ratio) of 0.76, that is, thephotosensitive layer had a very high sensitivity and showed a very highresolving power. Further, the light transmittance of the pattern at 400nm was 70%, which showed the pattern having a transparency. When thepattern was heat-treated at 280° C. for one hour, the residual layerthickness ratio was 83% and the extent of the heat shrinkage thereof wasless.

Comparative Example 1

By following the same procedure as in Example 1 except that the compoundPBG-1 as the photodecomposable base generator was not used, aphotosensitive layer was formed and the formation of a negative-typepattern was tried in the same manner as in Example 1.

However, the photosensitive layer was wholly dissolved at development,and a negative-type pattern could not obtained. Further, even when theirradiation amount of the actinic rays was increased to 500 mJ/cm² thesolubility at development was not changed and a negative-type patterncould not be obtained.

Comparative Example 2

By following the same procedure as in Example 1 except that 20 parts ofnifedipine was used in place of the compound PBG-1 used as thephotodecomposable base generator in Example 1, a photosensitive layerwas prepared and the formation of a pattern was tried.

However, the photosensitive layer was wholly dissolved in toluene atdevelopment, and a pattern could not be obtained. Further, even when theirradiation amount of the actinic rays was increased to 500 mJ/cm², theexposed portions of the photosensitive layer were dissolved slightlyfaster than the unexposed portions to cause a difference in solubilitybetween those portions, but a clear pattern (positive-type pattern)could not be obtained.

Comparative Example 3

By following the same procedure as in Example 1 except that 20 parts of2,6-di(p-azidobenzal)-4-methylcyclohexane was used in place of thecompound PBG-1 used as the photodecomposable base generator in Example1, a photosensitive layer was prepared and the formation of a patternwas tried.

A pattern having an aspect ratio of 0.4 could be formed at a sensitivityof 200 mJ/cm², but the light transmittance of the pattern at 400 nm was15% and the pattern was severely colored. When the pattern was themheat-treated at 260° C. for one hour, the residual layer thickness ratiothereof was 78% and the surface of the coated layer was partiallycracked by curing shrinkage.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A heat-resistant photoresist compositioncomprising a resin component having a carbodiimide unit represented bythe following formula (I), and a compound capable of inducing a basiccompound by irradiation with actinic rays,

    .brket open-st.R-N=C=N.brket close-st.                     (I)

wherein R represents a divalent organic group.
 2. The heat-resistantphotoresist composition as claimed in claim 1 wherein the resincomponent is a polycarbodiimide compound.
 3. The heat-resistantphotoresist composition as claimed in claim 2, wherein thepolycarbodiimide compound has a number average molecular weight of from300 to 300,000.
 4. The heat-resistant photoresist composition as claimedin claim 1, wherein the resin component contains carbodiimide units inan amount of from 20 to 100 mol %.
 5. The heat-resistant photoresistcomposition as claimed in claim 1, wherein the compound capable ofinducing a basic compound by irradiation with actinic rays is at leastone selected from the group consisting of a carbamate derivativerepresented by the following formula (II) and a carbamate derivativerepresented by the following formula (III); ##STR4## wherein R₁, R₂, andR₃ each represents a hydrogen atom or a methoxy group; R₄ and R₅ eachrepresents a hydrogen atom or a nitro group and at least one of R₄ andR₅ is a nitro group; R₆ represents a hydrogen atom or a lower alkylgroup having from 1 to 6 carbon atoms; and X represents a monovalentamine residue for carbamate bonding; ##STR5## wherein R₁, R₂, and R₃each represents a hydrogen atom or a methoxy group; R₄ and R₅ eachrepresents a hydrogen atom or a nitro group and at least one of R₄ andR₅ is a nitro group; R₆ represents a hydrogen atom or a lower alkylgroup having from 1 to 6 carbon atoms; and Y represents a divalent amineresidue for dicarbamate bonding.
 6. The heat-resistant photoresistcomposition as claimed in claim 5, wherein the carbamate derivativeconsists of an amount of from 0.001 per 100 parts by weight to 100 partsby weight of the resin component.
 7. The heat-resisting photoresistcomposition as claimed in claim 1, wherein the actinic rays areultraviolet rays.